This invention relates to the field of display devices and more particularly to computer terminals and word processors which provide data to people with impaired or no vision.
Throughout the world, millions of people have impaired vision and are able to read, if at all, only enlarged, high-contrast images. Many other people cannot read at all and therefore must rely on their sense of touch using tactile devices or their sense of hearing using audible devices. Consequently, people with such impairments cannot easily use the commonly available displays associated with computers, word processors and other data processing equipment.
In order to enhance the use of data processing displays by the visually impaired, various special systems have been developed. For example, television cameras have been used to detect and magnify images from a CRT (cathode ray tube) screen. The televised image of the CRT screen is displayed in enlarged form on a separate television screen. Although such television systems do provide some help to people with poor vision, they exhibit poor machine and human interactive operation, primarily because such television systems do not have the ability to automatically find or track a cursor in the CRT image.
Special display systems have been designed for use by the visually impaired and the blind. These special systems convert display data to enlarged characters for easier viewing, to tactile images for feeling or to speech for hearing. Such special systems, however, do not generally allow the use of conventional programs and terminals. For these reasons, the special systems have been expensive compared with conventional systems for fully-sighted people.
Conventional systems for fully-sighted people have two components. One component is a digital image generator which generates image signals which represent an image to be displayed. The other component is a display device which receives the generated image signals and responsively forms the displayed image for human viewing.
In a typical and conventional CRT display device, the generated image signals include a video data signal, a horizontal synchronization signal and a vertical synchronization signal. The video data signal is modulated to be either a digital "1" or a digital "0" directing the CRT beam to be turned on or turned off as the CRT beam is scanned across different locations of the display screen. The generated image signals are converted by the display device to a human-viewed displayed image. A television monitor is a typical display device familiar to most everyone. There is a one-for-one bit mapping of the bits in the generated image signal to bits in the displayed image.
In order to facilitate machine/human interaction, the image generator through a digital processor and keyboard, or other human-controlled input device, generates a cursor for signalling a specific location in the displayed image. Frequently, the cursor appears as an underline of a character, a blinking image, or other visually detectable signal. The location of the cursor in the displayed image is utilized by a human operator as a reference location for making changes in the displayed image.
The use of a cursor together with other control functions has proven very useful for fully sighted people. People with vision impairment, however, have great difficulty in seeing the displayed image or the cursor and therefore have been excluded from usefully functioning with conventional equipment in the data processing field.
In accordance with the above background, there is a need for a device to adapt conventional and readily available display systems for use by people with impaired or no vision.